"Climate change is real, as I've often said, and we should take strong action against it. But these fires are certainly not a function of climate change, they're a function of life in Australia," declared the Prime Minister.

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PM Tony Abbott with members of the Davidson fire brigade after helping with a backburining operation near Bilpin, NSW.Credit:Laura Jayes/Sky News Australia

But is that the advice Mr Abbott is getting from the experts at his disposal?

Environment Minister Greg Hunt has been briefed this week by the Bureau of Meteorology about the NSW fires, and that wouldn't be its advice.

Risks rise

As the bureau told a Senate inquiry into extreme weather events earlier this year: "The Forest Fire Danger Index (FFDI), which essentially 'sums' daily fire weather danger across the year, has increased significantly across many Australian locations since the 1970s.

Hot topic: a surge of bushfires across NSW has sparked a debate on climate change.Credit:Wolter Peeters

"The number of locations with significant increases is greatest in the southeast, while the largest trends occurred inland rather than near the coast. The largest increases in seasonal FFDI have occurred during spring and autumn. This indicates a lengthened fire season."

Mr Hunt did, though, point to a hotly debated link in the climate-bushfire chain.

"Senior people at the Bureau of Meteorology” take a precautionary line, Mr Hunt said. “They always emphasise never trying to link any particular event to climate change."

Actually, Mr Hunt is slightly off the mark. To say that such a link can “never” be made is only true if you add the words “right now”.

In fact, climate scientists around the country and beyond will already have pointed their super-computers towards identifying a signal from the changing climate system.

Heating up

Australia's famously variable climate makes it difficult to prove any major event is caused by climate change, only that the odds of it happening without a warming background would be less. It would be at least as hard to rule it out as "hogwash".

Temperature is one of the key factors influencing fire danger ratings - along with wind, humidity, and dryness of the fuel load.

The science is less certain about wind and humidity trends, but hotter temperatures are among Australia's clearest climate signals. It's not a huge leap to figure that hotter temperature would tend to dry out fuel loads more than cooler ones.

And you don't need to be a climate scientist to observe a clear warming trend - assuming, of course, you accept the integrity of the Bureau and the CSIRO.

Australia has warmed up by roughly 0.7 degrees nationally since 1960, the two organisations say.

See the per-decade shift here:

But we're a big country and have seasons, so it's worth looking at spring maximums, since that's the current problem in NSW and also the season when the rate of warming happens to be fastest:

So Australia is getting hotter, especially NSW in spring.

Complexity

Bushfire experts such as Hamish Clarke, Christopher Lucas and Peter Smith, have examined the data from weather stations across the country where the data is considered of sufficient quality and duration.

Between 1973 and 2010, they found the Forest Fire Danger Index (FFDI) – the measure used by fire authorities to determine whether the day will have a “low/moderate” to “catastrophic” fire danger – increased significantly at 16 of the 38 stations during the period. Not one registered a decrease.

The FFDI is complex, not least because it combines meteorological data and dryness of fuel. (For Sydney this year, July-October will smash records for average maximums, with each month the hottest or second hottest on record, while much of the eastern part of the state has been very dry since mid-June after a couple of wet years.)

That complexity is one reason why it's unwise to jump to a precise attribution of the NSW fires to global warming - but also why it's absurd to rule it out completely.

Heatwaves

Sarah Perkins, an expert in heatwaves at the ARC Centre for Excellence in Climate System Science at the UNSW, can understand why some blanch at discussing climate change amid the past week's destructive fires, with hundreds of homes lost and thousands of lives disrupted.

But it's an issue that's unlikely to go away. (Even Mr Abbott's mentor and then-PM John Howard made such a prediction back in 2006.)

“The eastern half of Australia is seeing an increase in the number of heatwave days,” Dr Perkins said, with heatwaves defined as three consecutive days when temperatures are in the top 10 per cent of warmth for that particular day.

“Those heatwaves outside summer are actually increasing faster than summertime events,” said Dr Perkins. “That is quite worrying for bushfire events and bushfire risk because it can induce this earlier drying of the fuel load.”

“It's more likely that these conditions will continue more often in spring, in the future,” Dr Perkins said.

NSW, of course, is hardly alone.

Roger Jones, a researcher at Victoria University and former CSIRO scientist, says levels of fire dangers "have done the same thing as extreme temperatures".

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For Victoria, that means the FFDI is about a third higher since 1996-97 than before. "That's generally not recognised," Dr Jones said, who is also a co-ordinating lead author for the latest report by the Intergovernmental Panel on Climate Change.

Dr Jones' work for the IPCC focused on decision making, aimed at resolving perhaps the most challenging link of them all - how to connect policymakers with the overwhelming findings of climate science.